> 2)Can I expect it to run at 60fps in mame and be as smooth as in Viva?

No, see above.

> 1)is it true that some model 2 games are now running in mame?

Yes but only 2D graphics, you need Model2 emulator from http://nebula.emulatronia.com if you want to be able to play some Model2B/2C games with 3D graphics/sound/force feedback (some are smoother/more playble than others).

> 2)Is it true Indy 500 is playable in mame?

No, no 3D yet, plus will be slower than Model2 emulator. In M2 emulator it runs pretty much full speed on my PC though I have some graphics glitches as the emulator prefers Nvidia cards.

> 3)How fast will it run on a 3Ghz machine?

See above, cannot say for MAME as emulation is incomplete.

> 4)Best graphics card to use with mame?

Irrelevant, everything is drawn by the processor - graphics cards can do some final DirectDraw/Direct3D effects but don't increase emulation speed in MAME.

By the way, some Model3 games are sneaking into MAME if you didn't know. Scud Race and Sega Bass Fishing are playable but very slow with lots of graphics issues (warping textures mainly).